The present invention relates to a vehicle wheel hub bearing unit.
It is known that the part of the bearing of a vehicle wheel hub must be fixedly connected to the disc or drum brake member so as to transmit the braking torque form the brake to the wheel.
FIGS. 1 and 2 are partial axial cross-sections illustrating two conventional solutions with disc and drum brakes, respectively, applied to flanged bearings of the so-called II generation. Similarly, disc or drum brakes can be applied to the so-called II generation bearings. In both the illustrated solutions the wheel rim, the brake member flange and the bearing flange are axially overlapping so as to interpose the brake member flange between the rim and the bearing flange. These three bodies are jointed by screwing the wheel bolts with the prescribed tightening torque.
Tightening of the bolts causes axial compression of the central portion of the wheel rim on the brake flange and of the latter on the bearing flange. This coupling arrangement has a drawback in that owing to geometrical defects such as planarity errors of the central part of the wheel rim, tightening of the bolts causes deformation of the braking surface and the bearing races.
A further drawback occurring is due to radial centering clearance of the brake/bearing coupling. Planarity errors of the relevant flanges concur in deforming the braking surface on tightening said bolts.
It is an object of the present invention to provide a vehicle wheel hub bearing unit which allows to obviate the above discussed inconveniences. Particularly, it is desired to provide a coupling system between the bearing and the brake member wherein tightening of the wheel bolts does not adversely affect the bearing races and the braking surface.
It is another object of the present invention to provide a coupling arrangement between the brake member and the bearing having a reduced axial bulk.
A further object of the present invention is to provide a coupling arrangement which, although reducing axial bulk as compared to prior art, allows to mount a bearing flange which is thicker and, consequently, less likely to undergo deformation caused by the coupling to a non-planar rim.
In accordance with one aspect of the invention as claimed, these objects are accomplished by the provision of a vehicle wheel hub bearing unit of the type in which the bearing forms a rotating radial flange adapted for securing to a radial flange of a brake member and rotate fixedly therewith, characterised in that the brake flange is located in the same radial plane of the bearing flange and secured directly to the peripheral portion thereof.